For manufacturing of metal sheets used as exterior décor panels for home appliances, there are various methods of forming a pattern to provide surfaces of the metal sheets with aesthetic effects, such as film attachment, printing, etching, rolling, and the like.
Among the aforementioned methods, attachment of a patterned film to a surface of a metal sheet can include attaching a film having various precise patterns on the appliance. Printing of a pattern on a surface of a metal sheet can include silkscreen printing, gravure printing or the like.
Etching and rolling differ from attachment of a film to or formation of a printing layer on a surface of a metal sheet in that a pattern is formed by directly processing a metal sheet. In the case of etching, after masking a surface of a metal sheet by photolithography, an unmasked patterned portion of the metal sheet may be etched using an etching solution. In the case of rolling, as a metal sheet passes through a rolling apparatus including a roller provided with a convex stereoscopic pattern, a stereoscopic pattern is formed on a front surface of the metal sheet. Rolling pressure of about 50˜60 tons may be required in some cases to form a pattern on a front surface of a metal sheet, such as a stainless steel, by rolling the front surface.
Brilliant surfaces may be acquired by polishing surfaces of fastening members, such as bolts and nuts, or metal workpieces, such as photo composers. Surface polishing techniques include mechanical polishing using a grinder as well as electrolytic-polishing in which current is applied to a workpiece dipped in an electrolytic bath.